Data communication quality control system, transmitter system and receiver

ABSTRACT

The object of the present invention is to insure the communication quality best suited to the type of data between the transmission system and the receiver. In the wireless communication system  1  for controlling the data communication quality between the transmission system  2  to transmit contents and the mobile wireless terminal  8  to receive contents from said transmission system  2  via the predetermined communication path  15,  since the transmission system  2  changes the modulation system in the data output unit  13  corresponding to the type of contents to be transmitted to the mobile wireless terminal  8,  the data communication quality between said transmission system  2  and the mobile wireless terminal  8  can be controlled. Thereby, the data transmission from the transmission system  2  to the mobile wireless terminal  8  can be executed according to the modulation system best suited to the type of contents holding the predetermined communication quality.

TECHNICAL FIELD

[0001] The present invention relates to a data communication qualitycontrol system, a transmission system and a receiver and is suitablyapplied to a wireless communication system comprising a base station fortransmitting contents data such as images or audio via a server, and amobile wireless terminal for receiving contents data from said basestation.

BACKGROUND ART

[0002] Heretofore, in the wireless communication system comprises a basestation and a mobile wireless terminal, the wireless communicationchannel is established between the base station and mobile wirelessterminal, and the data communication for various application data suchas sound, text or images are to be executed via said wirelesscommunication channel.

[0003] Furthermore, in the wireless communication system, the volume ofcommunications is not fixed since transmission condition varies frommoment to moment due to various effects in the wireless communicationpath between the base station and the mobile wireless terminal.Accordingly, the wireless communication system transmits the applicationdata from the base station at the fixed transmission speed set by saidbase station so that the bit error rate of the data to be transmittedbecomes lower than the predetermined rate.

[0004] However, in the wireless communication system thus constructed,the application data is transmitted from the base station to the mobilewireless terminal at the transmission speed just to make the bit errorrate lower than the fixed rate. And this does not cope with the casewhere the reliability of data is required although the transmissionspeed is low according to the type of application data or the case wherethe high transmission speed is required although the reliability of datais somewhat low. And this could not necessarily be said that it wasoffering the communication quality that the user desired.

DISCRIPTION OF THE INVENTION

[0005] The present invention has been done considering the above pointsand is proposing a data communication quality control system, atransmission system and a receiver capable of assuring the optimumcommunication quality suited to the type of data.

[0006] To obviate such problems according to the present invention, inthe data communication quality control system to control the datacommunication quality between the transmission system to transmit dataand the receiver to receive the data from said transmission system viathe predetermined communication path, since the transmission systemchanges the modulation system corresponding to the type of data to betransmitted to the receiver, the data communication quality between saidtransmission system and the receiver will be controlled.

[0007] With this arrangement, the data transmission can be executed fromthe transmission system to the receiver holding the predetermined datacommunication quality according to the modulation system best suited tothe type of data.

[0008] Furthermore, in the data communication quality control system tocontrol the data communication quality between the transmission systemfor transmitting data and the receiver for receiving data from saidtransmission system via the predetermined communication path, since thetransmission system adjusts the volume of data storage of thetransmitting side that temporarily conducts buffering when sending saiddata to the receiver corresponding to the type of data to be sent to thereceiver, and the receiver adjusts the data received from thetransmitter, i.e., adjusts the data storage volume of the receiving sidethat temporarily conducts buffering to the same data storage volume asthe data storage volume of the transmitting side, the data communicationquality between said transmission system and the receiver will becontrolled.

[0009] Thus, since the data can be read out at the optimum data readouttiming corresponding to the type of data by the receiver and can bedecoded, the data transmission can be effectively conducted holding thedata communication quality best suited to the type of data and notgenerating underflow or overflow from the transmission system to thereceiver.

[0010] Furthermore, according to the present invention, in the datacommunication quality control system to control the data communicationquality between the transmission system to transmit data and thereceiver to receive data from said transmission system through thepredetermined communication path, since the transmission system adjuststhe number of retransmissions when transmitting said data to thereceiver corresponding to the type of data to be transmitted to thereceiver, the data communication quality between said transmissionsystem and the receiver will be controlled.

[0011] With this arrangement, the data transmission from thetransmission system to the receiver can be conducted holding thepredetermined data communication quality according to the number ofretransmissions best suited to the type of data.

BRIEF DESCRIPTION OF DRAWINGS

[0012]FIG. 1 is a schematic diagram showing the general construction ofa wireless communication system according to one embodiment of thepresent invention.

[0013]FIG. 2 is a brief linear block diagram showing the circuitconstruction of a wireless communication system according to the firstembodiment.

[0014]FIG. 3 is a characteristic curvilinear diagram showing therelationship between the CIR and the transmission speed.

[0015]FIG. 4 is a flow chart showing the modulation control processingprocedure corresponding to the type of contents by the mobile wirelessterminal.

[0016]FIG. 5 is a flow chart showing the modulation control processingprocedure corresponding to the type of contents by the transmissionsystem.

[0017]FIG. 6 is a brief linear block diagram showing the circuitconstruction of a wireless communication system according to the secondembodiment.

[0018]FIG. 7 is a flow chart showing the buffer size control processingprocedure corresponding to the type of contents.

[0019]FIG. 8 is a characteristic curvilinear diagram showing therelationship between the buffer size and the relay time.

[0020]FIG. 9 is a characteristic curvilinear diagram showing therelationship between the buffer size and the packet loss.

[0021]FIG. 10 is a brief linear block diagram showing the circuitconstruction of a wireless communication system according to the thirdembodiment.

[0022]FIG. 11 is a flow chart showing the control processing procedureon the number of packet retransmissions corresponding to the type ofcontents.

[0023]FIG. 12 is a characteristic curvilinear diagram showing therelationship between the number of packet retransmissions and the delaytime.

[0024]FIG. 13 is a characteristic curvilinear diagram showing therelationship between the number of packet retransmissions and the packetloss.

BEST MODE FOR CARRYING OUT THE INVENTION

[0025] The present invention will be described in detail with referenceto the accompanying drawings.

[0026] (1) General Construction of Wireless Communication System

[0027] In FIG. 1, 1 generally shows a wireless communication system as adata communication quality control system according to the presentinvention. And this comprises a transmission system 2 to transmitcontents and a mobile wireless terminal 8 to receive contents from saidtransmission system 2 as a receiver and display this.

[0028] The transmission system comprises a server 3 for providingcontents and a base station 4 for transmitting the contents suppliedfrom said server 3 to the mobile wireless terminals 8, and thecommunication quality between the base station 4 and the mobile wirelessterminal 8 can be controlled by said server 3.

[0029] The mobile wireless terminal 8 is a mobile telephone in thecellular system and establishing the wireless channel with the basestation 4 within the domain of cell in which said mobile wirelessterminal 8 itself exists, receives contents from the server 3 throughsaid base station 4.

[0030] (2) The First Embodiment

[0031] (2-1) Circuit Construction of Wireless Communication System

[0032] As shown in FIG. 2, firstly the server 3 enters contents data D1of the contents to be transmitted (such as moving picture, stillpicture, text or audio) into an encoder unit 11, and by compressionencoding the contents data D1 at the predetermened compression ratedesignated by the transmission control unit 14 comprised ofmicroprocessor forms coded data D2, supplies this to the data storageunit 12 of the base station 4.

[0033] The base station 4, after temporarily storing the coded data D2supplied from the encoder unit 11 of the server 3 in the data storageunit 12, sends this out to the data transmission unit 13 as the systemside transmission means.

[0034] The data transmission unit 13, adding an error correction code tothe coded data D2, packetizes this, and modulating this corresponding tothe control signal S1 from the transmission control unit 14 of theserver 3, forms a transmission data D3 and transmits this to the mobilewireless terminal 8 via the communication path 15.

[0035] The mobile wireless terminal 8 receives the transmission data D3by the data receiving unit 16 as the receiver side receiving means. Andconducting the demodulation processing and error correction processingmaking this as received data D4, it obtains a demodulation data D5, andafter storing this in the data storage unit 17, sends this out to thedecoder unit 18.

[0036] At this point, the data receiving unit 16, detecting the pilotsignal contained in said modulation data D5, calculates CIR (CarrierInterference Ratio) in the received data D4, and transmits this to thereceive control unit 20 comprised of microprocessor as a calculationresult data D5A of the CIR.

[0037] The receive control unit 20 monitors the data storage volume tobe stored in the data storage unit 17 from the data receiving unit 16.And at the time when the volume of data that can be decoded in thedecoder unit 18 is stored, the receive control unit 20 informs thedecoding timing to said decoder unit 18.

[0038] The decoder unit 18 decodes the demodulattion data D5 respondingto the decoding timing notice from the receive control unit 20, andoutputs the resultant decoded data D6 to the display unit 19, and bydisplaying its contents via said display unit 19, it makes the user viewand hear.

[0039] As shown in FIG. 3, when the user wants to limit the bit errorrate of the receive data D4 received via the communication path 15 to“1.0”% (standard) for example, the relationship between the CIR and thetransmission speed (kbps) can be calculated according to thepredetermined algorithm as shown in the bar graph.

[0040] In this case, when CIR is 0 [dB], if the data receiving unit 16of the mobile wireless terminal 8 receives the transmission data S3transmitted at the transmission speed of 153.6 [kbps] through thecommunication path 15, it is considered that the bit error rate of thereceive data D4 can be controlled lower than “1.0”% (standard).

[0041] More specifically, in order to limit the bit error rate to lowerthan “1.0”% (standard) it is necessary to use the modulation system oflow transmission speed as the CIR becomes lower in the transmissionsystem 2 side, and it is necessary to use the modulation system of hightransmission speed as the CIR becomes higher.

[0042] In the case of limiting the bit error rate to lower than “10”% or“0.1”%, it has the same relation as those of the above. However, in thatcase the difference occurs either the transmission speed requiredgenerally becomes higher or lower as compared with the case of limitingthe bit error rate to lower than “1.0”% (standard).

[0043] The receive control unit 20 determines whether the bit error rate“1.0” (standard) may be remained as it is corresponding to the type ofcontents (such as moving picture, still picture, text or audio) torequest to the transmission system 2, or high transmission speed isrequired although the bit error rate may be remained lower than “10”%,or high transmission speed is not required although high reliability of“0.1”% bit error rate is needed as occasion demands.

[0044] Then, the receive control unit 20 as the receiver sidetransmission means determines new transmission speed correctedcorresponding to the bit error rate determined (such as, when the CIR is0 [dB] and it wants to limit the bit error rate to lower than “10”%, itdetermines to 307.2 [kbps], or when the CIR is 0 [dB] and wants to limitthe bit error rate to less than “0.1”%, it determines 76.8 [kbps]) andmaking this as the corrected transmission speed it transmits a requestsignal S4 to the transmission control unit 14 as the control means inthe server 3 and the system side transmission means.

[0045] The transmission control unit 14 of the server 3 selects themodulation system transmittable at the corrected transmission speed(such as BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase ShiftKeying), 16QAM (Quadrature Amplitude Modulation) or 64QAM) requested bythe request signal S4 from the receive control unit 20 of the mobilewireless terminal 8 as occasion demands, and by sending out the controlsignal S1 showing its modulation system to the data output unit 13 ofthe base station 4, it can greatly improve the communication quality inthe transmission path 15 satisfying the transmission speed and the biterror rate corresponding to the type of contents.

[0046] (2-2) Modulation Control Processing Procedure Corresponding tothe Type of Contents by Mobile Wireless Terminal

[0047] More specifically, in the wireless communication system 1, themodulation control processing will be conducted between the transmissionsystem 2 and the mobile wireless terminal 8 according to the procedureas shown in FIG. 4.

[0048] Firstly, at the step SP1, the base station 4 of the transmissionsystem 2 transmits the transmission data D3 in which pilot signal iscontained to the mobile wireless terminal 8 by using the data outputunit 13, and moves to the following step SP2.

[0049] At the step SP2, the mobile wireless terminal 8, after detectingthe pilot signal in the receive data D4 received at the data receivingunit 16, calculates the CIR in said received data D4 based on the pilotsignal at the following step SP3.

[0050] At the step SP4, the mobile wireless terminal 8 calculates thetransmission speed in order to control the bit error rate lower than“1.0”% (standard) according to the relation between the CIR and thetransmission speed shown in FIG. 3 by the receive control unit 20 andmoves to the following step SP5.

[0051] At the step SP5, the mobile wireless terminal 8 determineswhether to keep the bit error rate “1.0”% as it is corresponding to thetype of contents (moving picture data, text data or audio data) to berequested from the receive control unit 20 to the server 31, or keep itlower than “10”% and require the high transmission speed, or making thebit error rate to lower than “0.1”%, require the high reliability asoccasion demands, and corrects the transmission speed based on thedetermined bit error rate and the CIR.

[0052] At the step SP6, the mobile wireless terminal 8 requests thecorrected transmission speed to the transmission control unit 14 of theserver 3 from the receive control unit 20, and moves to the followingstep SP7.

[0053] At the step SP7, the transmission control unit 14 of the server 3receives the request relative to the corrected transmission speed fromthe mobile wireless terminal 8.

[0054] At the step SP8, the transmission control unit 14 of the server 3determines the modulation system transmittable at the correctedtransmission speed. Then, by outputting the control signal S1 showingthat modulation system to the data output unit 13 of the base station 4,the transmission control unit 14 transmits the transmission data D3 fromthe base station 4 to the mobile wireless terminal 8.

[0055] At the step SP9, receiving the transmission data D3 transmittedfrom the base station 4 at the corrected transmission speed in the datareceiving unit 16, the mobile wireless terminal 8 can obtain the receivedata D4 that satisfies the optimum bit error rate suited to the type ofcontents.

[0056] (2-3) Modulation Control Processing Procedure Corresponding tothe Type of Contents by Transmission System

[0057] On the other hand, in the wireless communication system 1, it isalso possible that the modulation control processing between thetransmission system 2 and the mobile wireless terminal 8 would beexecuted by the control of the transmission system 2 side as shown inFIG. 5.

[0058] Firstly, at the step SP11, the base station 4 of the transmissionsystem 2 transmits the transmission data D3 in which the pilot signal iscontained to the mobile wireless terminal 8 by the data output unit 13,and moves to the following step SP12.

[0059] At the step SP12, after detecting the pilot signal in thereceived data D4 by the data receiving unit 16, the mobile wirelessterminal 8 calculates the CIR in said received data D4 based on thepilot signal at the following step SP13, and informs this to the receivecontrol unit 20.

[0060] At the step SP14, the mobile wireless terminal 8 calculates thetransmission speed to limit the bit error rate to lower than “1.0”%(standard) according to the relation between the CIR and thetransmission speed by the receive control unit 20, and moves to thefollowing step SP15.

[0061] At the step SP15, the mobile wireless terminal 8 requests thetransmission speed to limit the bit error rate to lower than “1.0”% tothe transmission control unit 14 of the server 3 from the receivecontrol unit 20, and moves to the following step SP16.

[0062] At the step SP16, the transmission control unit 14 of the server3 receives the request for the transmission speed from the mobilewireless terminal 8.

[0063] At the step SP17, the transmission control unit 14 of the server3 determines whether the bit error rate of “1.0”% would be kept as it isas required from the mobile wireless terminal 8 corresponding to thetype of contents (moving picture data, text data or audio data)requested from the mobile wireless terminal 8, or whether to make thebit error rate lower than “10”% and the high transmission speed isneeded, or making the bit error rate to lower than “0.1”% and the highreliability is needed instread of high transmission speed, and itcorrects the transmission speed based on the determined bit error rateand the CIR.

[0064] At the step SP18, the transmission control unit 14 of the server3 determines the modulation system that can be transmitted at thecorrected transmission speed, and outputting the control signal S1showing that modulation system to the data output unit 13 of the basestation 4, informs the corrected transmission speed determined to themobile wireless terminal 8 from the base station 4 at that correctedtransmission speed.

[0065] At the step SP19, the receive control unit 20 of the mobilewireless terminal 8, receiving the notification of correctedtransmission speed, assumes the modulation system in the data outputunit 13 of the base station 4 based on that corrected transmissionspeed, and conducts the preparation for demodulation processing by usingthe modulation system corresponding to said modulation system assumed.

[0066] At the step SP20, the transmission control unit 14 of the server20 determines the modulation system that can be transmitted at thecorrected transmission speed. And by outputting the control signal S1showing that modulation system to the data output unit 13, it transmitsthe transmission data D3 to the mobile wireless terminal 8 from the basestation 4 at the corrected transmission speed.

[0067] At the step SP21, the mobile wireless terminal 8, by receivingthe transmission data D3 transmitted from the base station 4 at thecorrected transmission speed in the data receiving unit 16, it canobtain the receive data D4 that can satisfy the optimum bit error ratesuited to the type of contents.

[0068] (2-4) Operation and Effects

[0069] According to the foregoing construction, in the wirelesscommunication system 1, the CIR in the receive data D4 will becalculated based on the pilot signal in the receive data D4 received atthe data receiving unit 16 of the mobile wireless terminal 8. And thetransmission speed will be determined to control the bit error ratelower than “1.0”% according to the relation between said CIR and thetransmission speed.

[0070] Then, in the wireless communication system 1, the bit error ratewill be determined by the mobile wireless terminal 8 or the transmissionsystem either to “1.0”%, “10”% or “0.1”% and the transmission speed willbe corrected based on that determined bit error rate and the CIR.

[0071] Then next, in the wireless communication system 1, thetransmission control unit 14 of the server 3 determines the modulationsystem transmittable at the corrected transmission speed, and outputsthe control signal S1 showing that modulation system to the data outputunit 13 of the base station 4, and transmits the transmission data D3from the base station 4 to the mobile wireless terminal 8 at thecorrected transmission speed.

[0072] With this arrangement, the mobile wireless terminal 8 can receivethe transmission data D3 having the transmission speed correctedcorresponding to the type of contents from the base station 4. And thus,the mobile wireless terminal 8 can obtain the receive data D4 thatsatisfies the communication quality (bit error rate) required for thetype of contents.

[0073] (3) The Second Embodiment

[0074] As shown in FIG. 1, the wireless communication system 20 comprisea transmission system 30 having a server 31 and a base station 4, and amobile wireless terminal 33.

[0075] (3-1) Circuit Construction of Wireless Communication System

[0076] In FIG. 6, in which corresponding parts of FIG. 2 are designedthe same reference numerals, the server 31 of the transmission system 30enters a content data D1 of the contents (such as moving picture, stillpicture, text or audio) to be transmitted into an encoder unit 11. Andby compression encoding the contents data D1 at the predeterminedcompression rate specified by the transmission control unit 32, it formsa coded data D2, and supplies this to the data storage unit 12 of thebase station 4.

[0077] The base station 4, after storing the coded data D2 supplied fromthe encoder unit 11 of the server 31 in the data storage unit 12temporarily, transmits this to the data output unit 13. The data outputunit 13, as well as adding error correction code to the coded data D2,packetizes this, and modulating this by the predetermined modulationsystem, forms a transmission data D3, and transmits this to the mobilewireless terminal 33 via the communication path 15.

[0078] The mobile wireless terminal 33 receives the transmission data D3by the data receiving unit 16, and by conducting the demodulationprocessing and the error correction processing on this as the receivedata D4, obtains a demodulation data D5, and after storing this in thedata storage unit 17 temporarily, it outputs this to the decoder unit18.

[0079] Incidentally, the receive control unit 34 monitors the volume ofdata storage to be stored in the data storage unit 17 from the datareceiving unit 16. And when the data volume that can be decoded in thedecoder unit 18 is stored, the receive control unit 34 informs thedecoding timing to said decoder unit 18.

[0080] The decoder unit 18 decodes the demodulation data D5 according tothe decoding timing notice from the receive control unit 20, and outputsthe resulting decoded data D6 to the display unit 19, and displayingcontents of the data via said display unit 19, it can make the user viewand hear.

[0081] By the way, the transmission control unit 32 of the server 31 cancontrol the volume of data storage of the coded data D2 to be stored inthe data storage unit 12 of the base station 4. And simultaneously, thetransmission control unit 32 can control the volume of data storage ofthe demodulation data D5 in the data storage unit 17 of the mobilewireless terminal 33 interlocking to said data storage unit 12.

[0082] (3-2) Buffer Size Control Processing Procedure Corresponding tothe Type of Contents

[0083] More specifically, in the wireless communication system 20 thebuffer size control processing onto the data storage unit 12 and thedata storage unit 17 will be conducted between the transmission system30 and the mobile wireless terminal 33 according to the procedure asshown in FIG. 7.

[0084] Firstly, at the step SP30, the mobile wireless terminal 33requests the type of contents to the transmission control unit 32 in theserver 31 of the transmission system 30 from the receive control unit20.

[0085] At the step SP31, the transmission control unit 32 of the server31, by sending a buffer size setting signal S6 to the data storage unit12, sets the data storage volume (buffer size) of the coded data D2 tothe data storage unit 12. And simultaneously, it designates the samedata storage volume as that of the data storage unit 12 to the datastorage unit 17 by transmitting said buffer size setting signal S6 tothe receive control unit 34 of the mobile wireless terminal 33.

[0086] At the step SP32, the mobile wireless terminal 33, by outputtingthe buffer size setting signal S6 to the data storage unit 17 from thereceive control unit 34, sets the data storage volume (buffer size) inthe case of storing the demodulation data D5 demodulated at the datareceiving unit 16 into the data storage unit 17 similar to that of thedata storage unit 12, and it moves to the following step SP33.

[0087] At this point, since the physical maximum data storage volume inthe data storage unit 12 and the data storage unit 17 has beendetermined, the setting of data storage volume (buffer size) means herethat the setting of usage pattern regarding write-in or read-out of thedata storage unit 12 and the data storage unit 17.

[0088] At the step SP33, since the mobile wireless terminal 8 set thebuffer size of the data storage unit 17 according to the specificationfrom the server 31, it requests starting of the data communication ofcontents to the server 31 via the base station 4 by the receive controlunit 34.

[0089] At the step SP34, the base station 4 starts the buffering to thedata storage unit 12 of the coded data D2 supplied from the encoder unit11 of the server 31 and moves to the next step SP35.

[0090] At the step SP35, in the case of reading out the coded data D2from the data storage unit 12 by the data output unit 13, the basestation 4 reads this out at the time when the coded data D2 for the datastorage volume set based on the buffer size setting signal S6 is stored,and it starts the data transmission of the transmission data D3 afterapplying the modulation processing.

[0091] At the step SP36, the mobile wireless terminal 33 receives thetransmission data D3 from the base station 4 as the receive data D4 fromthe data receiving unit 16, and moves to the following step SP37.

[0092] The mobile wireless terminal 33 of the step SP37 reads out thedemodulation data D5 at the read-out timing supposing that thedemodulation data D5 for the fixed data storage volume may be stored inthe data storage unit 17 according to the buffer size specified from theserver 31 and starts the decoding processing by the decoder unit 18.

[0093] At this point, as shown in FIG. 8, the relationship between thebuffer sizes (large, middle, small) in the case where the data storagevolumes (buffer sizes) of the data storage unit 12 and the data storageunit 17 are optionally set according to the buffer size setting signalS6 and the delay time of the transmission data D3 will be shown inFigure.

[0094] More specifically, in the relation between the buffer size andthe delay time, the probability that delay will occur when transmittingthe data to the mobile wireless terminal 33 from the transmission system30 is expressed in the delay time basis. Thus, it is clear from thisFigure, when the large buffer size is set, it takes long time to readout the coded data D2 after storing this. And if the small buffer sizeis set, it takes short time to read out the coded data D2 after storingthis.

[0095] Furthermore, as shown in FIG. 9, regarding the relation betweenthe buffer sizes (large, middle, small) and the packet loss, theprobability of ratio of packet loss will occur is expressed per ratio.And it is clear from this Figure that as the buffer size becomessmaller, the probability that the packet will occur becomes higher, andas the buffer size becomes larger, the probability that the packet losswill occur becomes lower.

[0096] This is caused by the fact that the data read-out timing from thedata storage unit 12 and the data storage unit 17 would become the samesince the transmission control unit 32 of the server 31 has set thebuffer sizes of the storage unit 12 of the base station 4 and the datastorage unit 17 of the mobile wireless terminal 33 to the same datastorage volume.

[0097] More specifically, in the case where the buffer sizes of thestorage unit 12 in the base station 4 and the data storage unit 17 ofthe mobile wireless terminal 33 are set larger than the normal standardsize, even if the sufficient data volume is not stored in the datastorage unit 17 of the mobile wireless terminal 33 caused by the datatransmission speed decrease due to worsening of the communicationcondition in the communication path 15 when the data transmission to themobile wireless terminal 33 is started from the base station 4 via thecommunication path 15 (step SP35, step SP36, step SP37), the probabilitythat underflow will occur decreases since the read-out timing fordecoding is slow for the portion that the buffer size is set large.

[0098] On the other hand, in the case where the buffer sizes of the datastorage unit 12 of the base station 4 and the data storage unit 17 ofthe mobile wireless terminal 33 are set smaller than the normal standardsize, if the data transmission speed decreases due to worsening of thecommunication condition in the communication path 15 and the sufficientvolume of data is not stored in the data storage unit 17 of the mobilewireless terminal 33 when the data transmission is started to the mobilewireless terminal 33 from the base station 4 via the communication path15 (step SP35, step SP36, step SP37), the probability of underflowoccurrence becomes high because the read-out timing for decoding is fastfor the portion that the buffer size is set small.

[0099] Thus, the transmission control unit 32 of the server 31, bycontrolling the data storage volume for the data storage unit 12 and thedata storage volume for the data storage unit 17 of the mobile wirelessterminal 33, can adjust the time required from storing the data throughreading it out. And thereby the occurrence of underflow will beprevented even when the data transmission speed in the communicationpath 15 decreases and the decoding error will be further decreased.

[0100] (3-3) Operation and Effects

[0101] According to the foregoing construction, the transmission controlunit 32 of the server 31 optionally sets the buffer size in the datastorage unit 12 of the base station 4 and the data storage unit 17 ofthe mobile wireless terminal 33 corresponding to the type of contents(moving picture data, text data or audio data) requested from the mobilewireless terminal 33 and arranges the time required from the write-inthrough read-out.

[0102] More specifically, if the transmission control unit 32 of theserver 31 sets the buffer size in te data storage unit 12 and the datastorage unit 17 smaller than the normal standard size, the delay time ofthe transmission data D3 from the base station 4 to the mobile wirelessterminal 33 becomes shorter. However, when the transmission speeddecreases due to worsening of the communication condition in thecommunication path 15, the read-out for decoding would be conductedunder the condition in which the demodulation data D5 is notsufficiently stored in the data storage unit 17 of the mobile wirelessterminal 33 and there is a possibility of occurrence of the underflow.

[0103] On the other hand, if the transmission control unit 32 of theserver 31 sets the buffer size in the data storage unit 12 and the datastorage unit 17 larger than the normal standard size, the delay time ofthe transmission data D3 from the base station 4 to the mobile wirelessterminal 33 becomes longer. However, even in the case where thetransmission speed decreases due to worsening of the communicationcondition in the communication path 15, the read-out timing becomesslower than the time when the buffer size is set small for that portion.And accordingly, the probability that the underflow will occur can bedecreased even if the readout for decoding would be conducted from thedata storage unit 17.

[0104] Thus, in the case where the data communication having highreliability suited to the type of contents is required, the transmissioncontrol unit 32 of the server 31 sets the buffer size in the datastorage unit 12 and the data storage unit 17 large. On the other hand,in the case where the high speed communication having short delay timerather than the reliability is required, the transmission control unit32, setting the buffer size in the data storage unit 12 and the datastorage unit 17 small, offers the optimum communication quality bestsuited to the contents of which the type is specified by the mobilewireless terminal 33.

[0105] According to the foregoing construction, by setting the buffersize in the data storage unit 12 of the base station 4 and the datastorage unit 17 of the mobile wireless terminal 33 corresponding to thetype of contents by the transmission control unit 32 of the server 31,the wireless communication system 20 can provide the optimumcommunication quality suited to the type of contents to the mobilewireless terminal 33.

[0106] (4) The Third Embodiment

[0107] As shown in FIG. 1, the wireless communication system 40comprises a transmission system 50 comprised of a server 51 and a basestation 4, and a mobile wireless terminal 53.

[0108] (4-1) Circuit Construction of Wireless Communication System

[0109] As shown in FIG. 10, in which the corresponding parts of FIG. 2are given the same reference numerals, the server 51 of the transmissionsystem 50 enters the contents data D1 of contents (such as movingpicture, still picture, text or sound) to be transmitted into theencoder unit 11. And by compression encoding the contents data D1 at thepredetermined compression rate specified by the transmission controlunit 52, the server 51 forms the coded data D2 and supplies this to thedata storage unit 12 of the base station 4.

[0110] The base station 4, after storing the coded data D2 supplied fromthe encoder unit 11 of the server 51 temporarily in the data storageunit 12, sends this out to the data output unit 13. The data output unit13, adding error correction codes to the coded data D2, packetizes thisand forms a transmission data D3 by modulating at the predeterminedmodulation system, and transmits this to the mobile wireless terminal 53through the communication path 15.

[0111] The mobile wireless terminal 53 receives the transmission data D3by the data receiving unit 16, and by conducting the demodulationprocessing and the error correction processing onto this as the receivedata D4, obtains a demodulation data D5. And after storing thistemporarily in the data storage unit 17, the mobile wireless terminal 53sends this out to the decoder unit 18.

[0112] In this connection, the receiving control unit 54 monitors thevolume of data storage to be stored in the data storage unit 17 from thedata receiving unit 16, and it can inform the decoding timing to saiddecoder unit 18 when the volume of data that can be decoded is stored inthe decoder unit 18.

[0113] The decoder unit 18 decodes the demodulation data D5 according tothe notice of decoding timing from the receive control unit 54, andoutputs the resulting decoded data D6 to the display unit 19. And bydisplaying the contents of data via said display unit 19, the decoderunit 18 makes the user view and hear this.

[0114] Then, the transmission control unit 52 of the server 51 is totransmit a retransmission control signal S8 to the data output unit 13of the base station 4 corresponding to the type of contents requiredfrom the mobile wireless terminal 33. With this arrangement, it cancontrol the number of packet retransmissions of the transmission data D3to be transmitted from said data output unit 13.

[0115] In this connection, it becomes the premise that the data storageunit 12 of the base station 4 has the volume of data storage to theextent that the overflow would not occur even in the case ofretransmitting the packet for the predetermined number of times in thedata output unit 13.

[0116] (4-2) Processing Procedure of Controlling the Number of PacketRetransmissions Corresponding to the Type of Contents

[0117] More specifically, the wireless communication system 40 executesthe processing for controlling the number of packet retransmissions ofthe transmission data D3 to be transmitted from the data output unit 13of the base station 4 between the transmission system 50 and the mobilewireless terminal 53 according to the procedure as shown in FIG. 11.

[0118] Firstly, at the step SP41, the mobile wireless terminal 53requests the type of contents to the transmission control unit 52 in theserver 51 of the transmission system 50 from the receive control unit54.

[0119] At the step SP42, the transmission control unit 52 of the server51, by outputting the retransmission control signal S8 corresponding tothe type of contents specified to the data output unit 13 of the basestation 4, sets the number of packet retransmissions in the data outputunit 13 corresponding to the type of contents.

[0120] At the step SP43, the data output unit 13 of the base station 4,by reading out the coded data D2 from the data storage unit 12 andapplying the modulation processing at the data output unit 13, startsthe data communication processing, and moves to the following step SP44.

[0121] At the step SP44, the data output unit 13 of the base station 4executes the data transmission, by repeatedly transmitting the packet ofthe transmission data D3 the number of packet retransmissionscorresponding to the type of contents to be transmitted based on theretransmission control signal S8 specified by the transmission controlunit 52 of the server 51.

[0122] At the step SP45, the data receiving unit 16 of the mobilewireless terminal 53 receives the transmission data D3. In that case, asshown in FIG. 12, it has a tendency that the more the number of packetretransmissions of the transmission data D3 becomes large, the delaytime till the correct decoded data D6 will be obtained becomes longer,and as the number of packet retransmissions becomes smaller, the delaytime becomes shorter.

[0123] Furthermore, as shown in FIG. 13, it has a tendency that as thenumber of packet retransmissions of the transmission data D3 increasesmore, the packet loss decreases, and as the number of packetretransmissions becomes smaller, the packet loss increases.

[0124] Accordingly, the decoder unit 18 of the mobile wireless terminal53 starts the decoding processing at the step SP46. At that time, whenthe number of packet transmissions is small, the delay time to get thedecoding result is short. However, the probability that decoding errorwill occur is high since the number of packet retransmissions is small.

[0125] On the other hand, when the number of packet retransmissions islarge, it takes longer delay time till the decoding result would beobtained. However, since the number of packet retransmissions is large,the probability that the decoding error will occur is low and thedecoded data D6 can be certainly restored.

[0126] (4-3) Operation and Effects

[0127] According to the foregoing construction, the transmission controlunit 52 of the server 51 controls the number of packet retransmissionsof the transmission data to be transmitted from the data output unit 13of the base station 4 corresponding to the type of contents (movingpicture data, text data or audio data, etc.) requested from the mobilewireless terminal 53.

[0128] More specifically, the transmission control unit 52 of the server51 sets the large number of packet retransmissions when the datacommunication with high reliability is required corresponding to thetype of contents. On the other hand, in the case where the high speedcommunication having short delay time is required rather than itsreliability, it sets fewer number of packet retransmissions. Thus, theoptimum communication quality suited to the request of contents typespecified from the mobile wireless terminal 53 can be assured.

[0129] According to the foregoing construction, since the wirelesscomunication system 20 controls the number of packet retransmissions bythe data output unit 13 of the base station 4 corresponding to the typeof contents by the transmission control unit 52 of the server 51, thecommunication quality best suited to the type of contents for the mobilewireless terminal 33 can be always guaranteed.

[0130] (5) Other Embodiments

[0131] The embodiments described above have dealt with the cases ofcontrolling only the modulation system as the first embodiment,controlling only the buffer size as the second embodiment, andcontrolling only the number of retransmissions or the retransmissiontime as the third embodiment. However, the present invention is not onlylimited to these but also the modulation system and the buffer size maybe combined and controlled, or the modulation system and the number ofretransmissions or the retransmission time may be combined, or thebuffer size and the number of retransmissions or the retransmission timemay be combined and controlled, or the modulation system and the buffersize and the number of retransmissions or the retransmission time may beall combined and controlled.

[0132] Moreover, the second embodiment described above has dealt withthe case of setting the volume of data storage (buffer size) of the datastorage unit 12 and the data storage unit 17 corresponding to the typeof contents requested from the mobile wireless terminal 33 as thereceiver. However, the present invention is not only limited to this butalso the volume of data storage (buffer size) may be set according tothe data error rate of the receive data D4 feedbacked by the receivecontrol unit 34 of the mobile wireless terminal 33.

[0133] Furthermore, the third embodiment described above has dealt withthe case of controlling the number of packet retransmissions by thetransmission control unit 52 of the server 51. However, the presentinvention is not only limited to this but also the number of packetretransmissions may be eventually controlled by adjusting the packetretransmission time required for packet retransmissions.

[0134] Furthermore, the first embodiment described above has dealt withthe case of calculating the CIR at the data receiving unit 16. However,the present invention is not only limited to this but also thedemodulation data D5 may be sent out to the receive control unit 54 andthe CIR may be calculated at said receive control unit 54.

[0135] Furthermore, the first˜the third embodiments described above havedealt with the cases of constituting servers 3, 31 and 51 by an encoder11 and transmission control units 14, 32 and 52. However, the presentinvention is not only limited to this but also the transmission controlunits 14, 32 and 52 may be provided in the base station 4 or these maybe provided in the supervisory base station that generally controls thebase station 4 and other base stations.

[0136] Furthermore, the embodiment described above has dealt with thecase of using mobile wireless terminals 8, 33 and 53 as the receivers.However, the present invention is not only limited to this but alsovarious other receivers such as the PDA (Personal Digital Assistant)having wireless communication capability and the personal computer maybe used.

[0137] According to the present invention as described above, a datacommunication quality control system, a transmission system and areceiver capable of executing the data transmission to the receiver fromthe transmission system by holding the predetermined communicationquality according to the modulation system best suited to the type ofdata can be realized.

[0138] Furthermore, according to the present invention, since data canbe read out by the receiver at the optimum read-out timing best suitedto the type of data and can be decoded, a data communication qualitycontrol system, a transmission system and a receiver capable ofexecuting the data transmission effectively not generating the underflowor overflow from the transmission system to the receiver holding thedata communication quality suited to the type of data can be realized.

[0139] Moreover, according to the present invention, a datacommunication quality control system, a transmission system and areceiver capable of executing the data transmission from thetransmission system to the receiver holding the predetermined datacommunication quality according to the number of data retransmissionsbest suited to the type of data can be obtained.

INDUSTRIAL UTILIZATION

[0140] The data communication quality control system, the transmissionsystem and the receiver of the present invention can be suitable appliedto the wireless communication system for controlling the communicationquality in the case of transmitting contents from such as the server tothe mobile wireless terminal via the base station.

1. A data communication quality control system for controlling the datacommunication quality between a data transmission system to transmitdata and a receiver to receive said data from said transmission systemthrough the predetermined communication path, wherein: said transmissionsystem; controls said data communication quality between saidtransmission system and said receiver by changing the modulation systemcorresponding to the type of said data to be transmitted to saidreceiver.
 2. The data communication quality control system according toclaim 1, wherein: said transmission system; uses the modulation systemthat can be transmitted at the high transmission speed in the case wherethe high reliability of said data is not required corresponding to saiddata type; and uses the modulation system that can be transmitted at thelow transmission speed in the case where the high reliability of saiddata is required corresponding to said data type.
 3. A transmissionsystem for transmitting data responding to the request of the receiverto said receiver, comprising: system side receiving means for receivinga request from said receiver; system side transmission means fortransmitting said data to said receiver; and control means forcontrolling the data communication quality between said transmissionsystem and said receiver by changing the modulation system correspondingto the data type suited to said request.
 4. The transmission systemaccording to claim 3, wherein: said control means; uses the modulationsystem that can be transmitted at the high transmission speed in thecase where the high reliability of data corresponding to the type ofsaid data is not needed; and uses the modulation system that can betransmitted at the low transmission speed in the case where the highreliability of data corresponding to the type of said data is required.5. A receiver for receiving the data requested from the transmissionsystem, comprising: receiver side transmission means for transmittingsaid request to the transmission system; and receiver side receivingmeans for receiving said data of which the data communication qualitybetween said transmission system and said receiver is controlled bychanging the modulation system corresponding to the type of said data.6. The receiver according to claim 5, wherein: said receiver sidereceiving means; in the case where the high reliability of said data isnot required for the type of data requested, it receives said data usingthe modulation system transmittable at the high transmission speed; andin the case where the high reliability of said data is required for thetype of data requested, it receives said data using the modulationsystem transmittable at the low transmission speed.
 7. A datacommunication quality control system for controlling the datacommunication quality between the transmission system to transmit dataand the receiver to receive said data from said transmission system viathe predetermined communication path, wherein: said transmission systemadjusts the volume of the transmitting side data storage to be bufferedtemporarily in the case of transmitting said data to said receivercorresponding to the type of said data to be transmitted to saidreceiver; and said receiver controls the data communication qualitybetween the transmission system and the receiver by adjusting thestorage volume of the receiving side data received from said transmitterto the same data storage volume as the data storage volume of saidtransmitting side.
 8. The data communication quality control systemaccording to claim 7, wherein: said transmission system; when the highreliability of said data corresponding to the type of said data is notrequired, it transmits said data in shorter time than the standard datacommunication time by setting the data storage volume of thetransmitting side smaller than the standard data communication timeinterlocking to the data storage volume of the receiving side; and whenthe high reliability of said data corresponding to the type of said datais required, it transmits said data in longer time than the standarddata communication time by setting the volume of data storage of thetrnasmitting side larger than said standard data communication timeinterlocking to the volume of data storage of the receiving side.
 9. Thedata communication quality control system according to claim 7, wherein:said transmission system adjusts the volume of data storage of saidtransmitting side and the volume of data storage of said receiving sideinterlocked according to the data error rate informed from saidreceiver.
 10. A Transmission system for transmitting data responding tothe request from the receiver to said receiver, comprising: system sidereceiving means for receiving a request from said receiver; system sidetransmission means for transmitting said data to said receiver; andcontrol means for controlling the data communication quality betweensaid transmission system and said receiver by adjusting the storagevolume of the transmitting side data to be buffered temporarily whentransmitting said data to said receiver to the almost same storagevolume of the receiving side data to be buffered temporarily in saidreceiver.
 11. The transmission system according to claim 10, wherein:said control means; when the high reliability of said data suited to thetype of said data is not required, it transmits said data in the shortertime than the standard data communication time by setting the volume ofdata storage of said transmitting side smaller than the standard datacommunication time interlocking to the volume of data storage of saidreceiving side; and when the high reliability of said data suited to thetype of said data is required, it transmits said data in the longer timethan the standard data communication time by setting the volume of datastorage of said transmitting side larger than the standard datacommunication time interlocking to the volume of data storage of saidreceiving side.
 12. The transmission system according to claim 10,wherein: said transmission system adjusts the volume of data storage ofsaid transmitting side interlocking to the volume of data storage ofsaid receiving side corresponding to the data error rate informed fromsaid receiver.
 13. A receiver for receiving the requested data from thetransmission system, comprising: receiving means of receiver side fortransmitting said request to said transmission system; and receivingmeans of receiver side for receiving said data of which the datacommunication quality between said transmission system and said receiveris controlled by adjusting the storage volume of the transmitting sidedata to be buffered temporarily when transmitting said data to saidreceiver corresponding to the type of said requested data to the samevolume as the storage volume of the receiving side data to be bufferedin said receiver.
 14. The receiver according to claim 13, wherein: saidreceiving means of receiver side; if the type of data requested wouldnot require the high reliability of said data, it receives the datatransmitted from the transmission system in the shorter time than thestandard data communication time by setting the volume of data storageof the transmitting side smaller than the standard data transmissiontime interlocking the volume of data storage of said transmitting sideto the volume of data storage of the receiving side; and if the type ofdata requested requires the high reliability of said data, it receivesthe data transmitted from said transmission system in the longer timethan the standard data communication time by setting the volume of datastorage of the transmitting side larger than said standard datacommunication time interlocking the volume of data storage of saidtransmitting side to the volume of data storage of the receiving side.15. The receiver according to claim 13, wherein: said receiving means ofthe receiver side; receives the data of which the data communicationquality between said transmission system and said receiver is controlledby adjusting the volume of data storage of the transmitting sideinterlocked to said volume of data storage of the receiving sidecorresponding to the data error rate informed from said receiver.
 16. Adata communication quality control system for controlling the datacommunication quality between the transmission system to transmit dataand the receiver to receive said data from said transmission systemthrough the predetermined communication path, wherein: said transmissionsystem; controls the data communication quality between saidtransmission system and said receiver by adjusting the number ofretransmissions in the case of transmitting said data to said receivercorresponding to the type of said data to be transmitted to saidreceiver.
 17. The data communication quality control system according toclaim 16, wherein: said transmission system; controls said datacommunication quality by adjusting the maximum number of retransmissionswhen transmitting said data to said receiver corresponding to the typeof said data.
 18. A transmission system for transmitting data respondingto the request from a receiver to said receiver, comprising: system sidereceiving means to receive the request from said receiver; system sidetransmission means to transmit said data to said receiver; and controlmeans to control the data communication quality between saidtransmission system and said receiver by adjusting the number ofretransmissions in the case of transmitting said data to said receivercorresponding to the type of data responding to said request.
 19. Thetransmission system according to claim 18, wherein: said control means;controls the data communication quality by adjusting the maximum numberof retransmissions in the case of transmitting said data to saidreceiver corresponding to the type of said data.
 20. A receiver forreceiving the requested data from the transmission system, comprising:receiver side transmission means for transmitting said request to saidtransmission system; and receiver side receiving means for receivingsaid data of which the data communication quality is controlled byadjusting the number of retransmissions in the case of transmitting saiddata to said receiver corresponding to the type of said requested datafrom said transmission system.
 21. The receiver according to claim 20,wherein: said receiver side receiving means; receives said data of whichthe data communication quality is controlled by adjusting the maximumnumber of retransmissions in the case of transmitting said data to saidreceiver corresponding to the type of said data to said request fromsaid transmission system.